The present invention relates to a method for controlling an auto-balancing system of an optic disk on an optic disk drive, and especially to a method by which the effect of friction force to a balancing mass can be reduced to a minimum so as to assure a preferred balance effect.
With the progress of optic information recording medium, the accessing speeds for optic disk drives used in the computer peripheral devices are increased in a very rapid ratio. Nowadays, the optic disk drive (CD-ROM) with a spindle motors having a rotary body over 10000 rpm has become a commercial primary products.
When the spindle motor rotates in a higher speed, the eccentric vibration due to unbalance of the optic disk becomes large so as to induce problems of vibration and noises.
In practical applications of optic disk drives, large vibrations will induce instabilities of the reading ability of the head so that the optic disk drive can not read data in a maximum rotary speed. Besides, for the use of an optic disk drive, the noise of an optic disk drive in a high rotary speed will induce some troubles.
Conventionally, in order to reduce the vibration due to the unbalance of the optic disk as the optic disk drive rotates in a high rotary speed, the manufacturer uses three methods for solving this problem, which are (1) directly increasing the weight of a reader for reducing vibration; (2) using a dynamic absorber in dynamics to reduce vibration; and (3) using an auto-balancing system for reducing vibration.
Aforesaid three ways all can be used to reduce the vibration quantity of the optic disk drive. In principle, the auto-balancing system has a preferred effect, since in that a balancing mass is used to reduce the stimulate energy of a vibration.
In current auto-balancing system used by the manufacturer of an optic disk drive, the auto-balancing system is added above (or blow) a spindle motor. The auto-balancing system includes a balancing mass (in general, steel balls of predetermined numbers) and a rotary body (a housing, in general having a round shape) for supporting the balancing mass. By principle of rotor dynamics, when the rotary speed of the spindle motor is higher than a critical speed, the position of the extra added mass will be at a position opposite to the unbalance vector of original optic disk. Thereby, the unbalance of the optic disk can be cancelled and thus, the vibration of the optic disk drive is reduced.
However, in fact, some confinement in manufacturing, such as real roundness, concentricity, coarseness and other factors induce the effect in application is not as good as that prediction from theory. In these factor, the friction force relates to a surface coarseness has a direct effect to the result of the balancing mass moving from an initial position to a ideal position.
Therefore, it is appreciated that the prior art auto-balancing system in an optic disk drive has some defect which is eagerly to be improved, and thus a novel method for controlling an auto-balancing system of the optic disk in an optic disk drive is required for solving these problems.
Accordingly, the primary object of the present invention is to provide method for controlling an auto-balancing system of the optic disk in an optic disk drive. Thereby, the vibration due to an unbalance of the optic disk during operation of an optic disk drive is reduced by an effective and steady method. As a result, the objects of reading data with high and accurate speed and operation smoothly are achieved.
In order to achieve aforesaid object, the present invention provides a method for controlling an auto-balancing system of an optic disk in an optic disk drive. In order to reduce the friction force of the balancing mass, as the rotary speed of a spindle motor is not faster than a critical speed, a dither signal is added to a command signal for speeding a maximum rotary speed. Then the balancing mass successfully moves to a position with a reverse phase opposite to an unbalance vector of the optic disk. After the rotary speed of the spindle motor is higher than a critical speed, the dither signal and then speeding the spindle motor is removed and the motor is accelerated to a maximum rotary speed.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when reading in conjunction with the appended drawing.